Always knew my hatch was getting optimal gas mileage but I just found out it's WAY off.

I got less than 200 miles in my last tank!! About 190 to be more exact.

I have a 91 std 4 speed manual. I do drive it semi hard on a daily basis. Things to note is that my car does burn a lot of oil. I think that makes the car run richer? I also have never changed the spark plugs either. I've owned the car for about 8 months now. I just find it hard to believe that my car could get less than 20 mpg.

Do ya really think it could get that bad because of the oil burning? I have another engine from a sedan that has more mileage but I think it isn't burning as much oil. Or would some sea foam help my hatch out? Thanks!

 

rebuild the motor top and bottom. thats your solution

 

I have a 91 Hatch with the stock 1.5 liter, MPFI, and a 5-speed Si transmission. I drove to Seattle and back yesterday and averaged 45 mpg. My last trip I averaged 49. That was driving conservatively and doing the speed limit. With city/highway mix I'm always above 30 even when I drive hard, usually around 37. Before when I had DPFI and the 4-speed it was about the same.

Do a good tune-up...plugs, wires, air filter, fuel filter...clean your IACV, check your tire pressure...when was the car last aligned? Do some of that stuff and see where you stand. Burning oil will affect fuel economy a little...I had to replace my piston rings and valve stem seals about 7-8 months ago but I was never below 20 mpg.

Sea Foam is a good preventative treatment but I've never seen a huge difference...I use it but it's not a magic cure.

 

Yeah, it very well may come to that but I would do those little things first. You said that you've owned the car for 8 months? A basic tune-up is in order. A lot of people questioned my decision to rebuild as opposed to doing a swap. I bought this car for a daily driver and fuel economy was a priority. Now it runs perfectly, doesn't leak or burn oil, and gets over 40 mpg. At least I'm certain of the condition. I did all the gaskets/seals, belts, water pump, alternator, etc. I expect it to run well for quite a while as long as I keep up on the regular maintenance.

At some point you're going to have to address the issue of it burning oil. If you're holding out for a swap or something a basic tune-up may improve the fuel economy until you can move on to bigger and better things.

 

A rebuild would be nice but I don't have enough monies for that. Considering a swap but for now I think the tune up is the way to go for me now. Also, I tend to always run my tank til it is completely out so I'm sure my fuel filter is pretty dirty by now. I will keep ya posted. Gracias EF amigos!

 

A rebuild is pretty expensive and a waste of time if you're planning a swap. A tune-up should be automatic with a used car but it is an investment as well...NGK plugs and wires about $40, a fuel filter probably another $15-$20...air filter probably $10 for a stock one...oil and filter $30. I would set aside $100 and see if you can get it running better. It would be worth it to check the alignment. Come up with a plan and do what makes sense. I know I have wasted money either by buying something cheap then buying what I really wanted later and just not having a plan as to what I wanted the end result to be. Keep in mind that you need to plan for the MPFI conversion before your swap as well.

I sunk a ton of money into my car but my plan was to have a super reliable daily driver that gets good fuel economy. That's not everyone's plan.

 

Your best bet for a cheap swap with reliability and fuel economy, plus a little fun in the power department, is to get a JDM D15. No, not like the dpfi D15... 1.5L VTEC 127hp.

http://www.hmotorsonline.com/shop/sc...age&item=30021

You don't need the transmission, it will bolt up to your current transmission. Replace the clutch when you swap. It's one of those things you might as well do since the car is going to be apart anyways.

You'll need to convert to MPFI of course. It's a fun swap, similar to the D16y8 or D16z6.

$800 for a basically brand new motor... plus whatever else you want to replace.

 

I may look into that on down the road...I did the MPFI conversion and swapped my 4-speed for a 5-speed Si. Could be fun. What do you need to do to activate Vtec?

 

Are u really putting 10 gallons in at the pump? I know I fill up at 200 miles ( that's when its reading almost "E" ) but only takes about 6 gallons to fill her up. So get around 33 34mpg with my b20

 

It's a 12 gallon tank.

 

im gonna assume you have a fuel issue either in the guage or a ****ed up tank, cus im pretty sure your suppose to have a 10 gallon tank like most every other honda civic delsol integra and crx

 

I average 34mpg with a b20 I know mine runs a lil rich but not bad and I lay into the gas a lot. Wouldn't call mine a fuel issue. Maybe a reading issue But I'm not trying to run out of gas. And my back end sits lower than the front

 

Also I drive 91 crx hf

 

The HF has a smaller tank, and most of our cars are 11 gallon. The only accurate way to figure gas mileage is to top it off, drive it, top it off again. You don't have to go to Empty. Miles driven divided by gallons added = mpg.

A tune up is worth it, even if you rebuild or buy a similar motor later.

 

Actually I just filed up its probly more so I fill up at a quarter tank. But anyways yes I would do a tune up. If u want your car to last a long time pick a engine up from hmotorsonline. That where I got mine. And I love it and runs brand new.

 

i would agree. its a little pricey from them, rather than buying local. but you know its legit and in running condition. plus you get EVERYTHING from them. ordered two engines from them so far. and still going strong

 

So you had a dual point d15 and did the MPFI swap and Si transmission?

EXACT same setup here with a completely rebuilt engine and tranny. I used to get 40+ MPG all day before my MPFI swap, and immediately after swapping the highest I could get was 35 all highway with no AC. Now that my work commute doesn't require a ton of highway driving I can normally only get 29-30 MPG, with no AC.

Now that it's summer time and I have to use the AC the entire time I'm only getting 26-27 MPG. That's ridiculous and really frustrates me. I can just about get that driving easy in my heavily modified Maxima.

I'm really at a loss what to do here. I replaced the 02 sensor a few tanks back because that was one of the few things that was still original, but it made no difference. Like I said, my engine and tranny are brand new (rebuilt). Burns no oil or any problems at all. My work commute is actually pretty ideal - even though I have no highway driving it's all 3-4 lane streets with 45 MPH speed limits and few stop lights. So you'd think my commute would actually be MPG friendly. I can't imagine what type of terrible mileage I'd get if I were in a typical stop and go commute.

 

Yes, I bought a STD with a stock D15B1, DPFI, and 4-speed manual a year ago. I did the MPFI conversion and swapped a 5-speed Si transmission. I feel like it gives me a little more power off the line and a little more power when passing but that's about it. The shop I was working with said that I'm probably somewhere around 96 hp but I don't know if it's accurate. I know I can feel a small difference and that's all that matters. Either way I'm set up for a future swap. Originally I bought the car as a cheap commuter so I've been hesitant to do anything to affect the fuel economy. The motor has been basically rebuilt...new rings, bearings, seals, gaskets, etc...it doesn't leak or burn any oil and is tuned up and running about as good as it's going to. Full tune-up, timing belt, new water pump and alternator. I also replaced all the suspension components, new tires, etc and did an alignment. It runs and drives so smooth. If I drive conservatively I can get +40 mpg all day long. I averaged 45 mpg on my last road trip and 49 the previous one. I am trying to break 50 but don't want to do anything crazy like strip the car. I will probably drive the car in this configuration for the next year or so and then do a swap for more power. Right now I enjoy the reliability and fuel economy too much to mess with it.

 

VTEC is wired to the ECU. When you get an OBD0-OBD1 jumper harness, it has a subharness with the necessary wires to run.

1 wire for VTEC oil pressure switch
1 wire for VTEC solenoid
1 ground wire for the oil pressure switch

4 wires for the o2 sensor (converting from your old 1 wire, forgot about this part!)

And you'll need to rewire distributor plug for OBD1 or get a jumper harness for that as well.

I bought my harness off Ebay from Zerg Industries. Worked all summer, worked all winter, no complaints.

96 hp is probably accurate, off the crank.
Any D series swap won't really affect fuel economy, but, DPFI gets better mpg than MPFI (unless you have the uber restrictive intake and stuff from the HF).
Si transmission will lower your MPG on the highway since you'll be sitting at like 3k going 60mph. I've heard of swapping in an LS 5th gear, but, it's a lot of work!!!
My old DPFI with 250,000kms on it could get 40-50mpg happily. I miss that car. Would never trade away my VTEC for it though!


Also this thread got jacked.


Si transmission is so fun. My buddy drives an EK and hates my short gears... only because his are so long.

 

I really don't like my MPFI/Si swap. It's given me no discernible power increase whatsoever other than the transmission gearing essentially forcing you to rag it to accelerate remotely fast (which isn't an actual power increase, of course). If I could do it all over again I'd have stayed stock and I'm too lazy revert. The entire car is essentially rebuilt/restored even new paint and carpet. I love the car but this MPG drop is killing me.

And boy, with the AC on, it feels like I'm carrying a car load of people. I mean it has noooo power.

 

All you guys getting 40+ mpg are killing me! I actually have another d15b2 engine in my garage but just like James89Dx says, the engine feels like im carrying a full load of people.

Gonna do a basic tune up and see where that takes me. I would like to get a z6 y8 or that D15B VTEC Canadian EF shared.

 

You might be surprised by the tune-up...if it doesn't work then you know you've got bigger problems. Honestly, I think you'llsee some improvement and buy yourself some time until you can do a swap or rebuild. If your alignment is off it will silently rob you of mpg and check your psi as well. It can get expensive but worn out suspension components kill you...deal with the more pressing stuff first.

 

I wonder if your oxygen sensor is dirty. Especially from all the oil you burn. Best thing to try is to replace it.

 

Our tanks are 11.9 gallons exactly.

His measurment for figuring out MPG is correct. Try to go to the same place, at the same time, at the same pump even for the most accurate reading.


sohc non vtech zc, si tranny, relatively new tune - average 31.5~ mpg. That's mixed city/highway. Best so far was 32.5mpg, all highway basically...

I also have about a mile of stop signs around my house so that kills me.

If you have an aftermarket fuel pump that's why you're refilling at around 4 gallons left. My car starts sputtering like it's out of gas @ about 4 gallons left - close to Empty anyways so I just fill up. But that's because ALL aftermarket fuel pumps that are NOT OEM have some stupid fuel pump sock that is angled wrong. There's a post on here that shows which one to actually get, the sock specifically. It's like an 88 dx fuel pump sock.

I'm too lazy to drop the tank again and replace the sock, rather just fill up more often anyways.

 

Get a prius.